<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        /* div span {
            color: red;
        } */
        /* 
            ::after在元素后面的内容添加一个伪元素
            ::before在元素前面的内容添加一个伪元素
            content属性设置伪元素中添加的内容
            样式都是修饰添加的内容
        */
        div::before {
            content: "《";
            color: aqua;
        }
        div::after {
            content: "》";
            color: red;
        }
        /* 
            ::selection用户在浏览器中选中文字触发的效果
        */
        div::selection {
            color: yellow;
        }
    </style>
</head>
<body>
    <!-- <div><span>《</span>html<span>》</span></div>
    <div><span>《</span>css<span>》</span></div>
    <div><span>《</span>js<span>》</span></div> -->
    
    <div>html</div>
    <div>css</div>
    <div>js</div>
</body>
</html>